The present invention relates to an apparatus for preparing beverages or other similar products using a food substance. The invention more precisely relates to dispensing machines, such as mobile or portable coffee machines.
The beverage preparation apparatuses of the coffee machine type which use prepacked or non-packed portions of a food substance are very widespread among private individuals, and also in municipalities, shopping centres and companies. The preparation principle is based on the extraction of portions of the substance by the passage through this substance of a quantity of cold or hot liquid under high pressure, typically a pressure above atmospheric pressure. The prepacked portions can be partially rigid capsules, or else flexible bags, which are hermetically sealed or partially open, or else a dose filter.
An example of a capsule is described in patent EP 0 512 468 B1. An example of a bag is described in patent EP 0 602 203 B1.
Such extraction systems have many advantages. On the one hand, the individual packages are easy to use and require no batching of coffee or other substances, in the machine. The user places a capsule, a ground-coffee dose or other portions in the machine, then presses a button to start extraction. On the other hand, the individual packages are batched to deliver a beverage, like a coffee, having the desired characteristics such as sufficient character, flavour, foam or other important attributes. When they are impermeable, they thus usually preserve the freshness of the substance better, up to the time of extraction. Finally, the preparation conditions, such as the temperature, pressure and extraction time can be better controlled, thereby guaranteeing relatively controlled and constant quality to the consumer.
An example of an extraction method is described in patent EP 0 512 470 B1.
To extract a beverage under pressure from these portions, of the capsule or other type, it is necessary to use a relatively powerful water pump such as an electric compressor. These pumps use the mains electric power supply. They are also rather noisy during extraction.
It is therefore difficult to move these preparation apparatuses, such as on a trolley or simply by carrying them. In fact, it would be an advantage to be able to make these apparatuses more mobile so as to offer beverages in locomotion means such as the train, plane, or in certain places such as cinemas, theatres, and also in public places such as beaches, parks, poolsides and other public or private places.
Patent application WO 99/02081 proposes a coffee machine, more precisely a mobile machine, in which the pressure required to extract the ground coffee is generated by compressed air. The water for preparing the coffee is kept in a thermally insulated container. The water can be heated by electric heating elements. This solution offers the advantage of producing the extraction pressure by a self-contained means, such as a gas cylinder, installed under the machine. The machine can be installed on a trolley with the gas cylinder installed in a compartment of the trolley provided for this purpose.
However, such a device presents certain drawbacks. In fact, in this invention, the gas of the cylinder communicates directly with the hot water tank. This means that the entire volume of the tank is kept under constant pressure, of the order of several bar.